British Patent Publications Nos. 2 111 394 A and 2 229 367 A describe artificial airway devices capable of facilitating lung ventilation in an unconscious patient, referred to hereinafter as "laryngeal masks". The insertion of a laryngeal mask needs to be undertaken by persons practised in the use of the mask and is not so effective in emergency situations where untrained personnel may be called to a patient. Furthermore, these devices suffer from the limitation that they do not offer the same degree of protection against aspiration of regurgitated gastric contents into the lungs as does an endotracheal tube. The latter device has long been established as the most reliable means of preventing such aspiration in the unconscious patient and consists of a tube with an inflatable cuff, inflation of which forms a seal against the wall of the trachea. The laryngeal mask by contrast forms a seal around the perimeter of the larynx by means of an inflatable elliptical cuff. The seal so formed depends on pressure against muscular structures which may by their contraction or relaxation Hence, the degree of protection against aspiration already afforded by the laryngeal mask would be enhanced by allowing intubation with an endotracheal tube, with the laryngeal mask in place. Attempts have been made to intubate through the airway tube of a conventional laryngeal mask and this has been found to be effective. However, only a small diameter endotracheal tube can be passed through the mask. Moreover, as the airway tube is flexible, the operation is awkward and not entirely suited to emergency procedures.